What percentage of strength to the hair is contributed by the cortex?

The cortex is the main component of the hair shaft and accounts for a significant portion of the hair's overall strength and structure. It is located between the cuticle (the outer layer) and the medulla (the innermost layer) and contains fibrous proteins and melanin, which contribute not just to strength but also to the hair's color and elasticity.

Research indicates that approximately 80% of the hair's strength comes from the cortex. This is because the cortex is composed of long chains of keratin, which provide durability and resilience to the hair. The organization and density of these protein structures in the cortex are crucial for how well the hair can withstand stress and damage from environmental factors, styling practices, and chemical treatments.

While the cuticle does play a role in protecting the hair and contributing to its overall appearance, it does not contribute significantly to the strength of the hair strand. The medulla, which is often absent in fine hair types, is typically not involved in the hair’s structural integrity. Therefore, understanding the central role the cortex plays is vital for those studying cosmetology, especially when it comes to hair care and treatments aimed at maintaining or improving hair strength.